This invention relates generally to an electrostatographic printer or copier, and more particularly concerns a cleaning apparatus used therein.
There are electrophotographic printing machines which use a conductive brush with a negative DC (direct current) bias. Toner charged positively by the preclean dicorotron is thus cleaned by rotating the biased cleaner brush. Detoning of the brush is accomplished with detoning rolls and a flicker bar/vacuum system. This cleaner has difficulty cleaning wrong sign toner and wrong sign paper debris. Blade cleaners are used in many copiers but are not usually used in high volume machines due to their poor reliability. A high toner Mass/Area (M/A) entering the blade cleaner creates a stress input. It has been demonstrated that if the M/A could be reduced, cleaning could be performed at lower minimum blade loads. Additionally, on other machines it has been determined that comet formation (i.e. small deposits, usually consisting of toner and toner additives, which cannot be cleaned from a surface and can grow to a size which creates copy quality defects) on the photoreceptor was reduced by decreasing the blade load, which would be possible if the M/A was reduced. In multicolor copiers and printers of the future, it is important to provide the most robust cleaner designs to assure acceptable cleaning performance over the wide variety of materials and conditions that will be encountered. In an effort to achieve this robust cleaner, some work has been done with a single conductive brush with an AC electrical bias to allow cleaning of both polarity toners with the same brush. This single AC biased brush has been shown to work well on occasion, but frequently redeposition of toner from the brush to the photoreceptor surface (i.e. imaging surface) occurs after the cleaner brush has been used to clean toner from the photoreceptor surface.
Other machines have developed dual brush ESB (electrostatic brush) cleaners, where the first brush is negatively biased and the second brush is positively biased. This type of cleaner is a robust cleaner for two polarities of toner and debris where one brush picks up one polarity and the other brush picks up the opposite polarity. In multicolor copiers and printers of the future, it is important to provide the most robust cleaner designs to assure acceptable cleaning performance over the wide variety of materials and conditions encountered.
The following disclosures may be relevant to various aspects of the present invention and may be briefly summarized as follows:
U.S. Pat. No. 4,999,679 to Corbin et al. discloses an apparatus for cleaning a photoconductive surface. The apparatus includes a pair of oppositely electrically biased cleaning brushes. Each brush is located in a separate housing with each housing electrically biased to the same polarity as the brush located therein.
U.S. Pat. Nos. 4,989,047 and 5,031,000 to Jugle et al. and Pozniakas et al., respectively, disclose cleaning apparatus including a negatively DC biased fiber cleaning brush serving as a primary cleaning member, a blade member serving as a secondary cleaning member, and a vacuum detoning arrangement for the brush.
U.S. Pat. No. 4,984,028 to Tonomoto discloses a cleaning unit including a rotatable fur brush, a cleaning blade and a suction means working in cooperation therewith.
U.S. Pat. No. 4,878,093 to Edmunds discloses a dual roll cleaning apparatus. A cleaning housing which is connected to a vacuum supports an upstream brush roll cleaner and a downstream foam or poromeric roll cleaner. The brush roll cleaner provides a primary cleaning function, while the foam roll cleaner provides a secondary back up cleaning function.
U.S. Pat. No. 4,967,238 to Bares et al. discloses a cleaning performance monitor. The monitor detects toner or debris deposits on an imaging surface downstream from a cleaning station.
U.S. Pat. No. 4,640,599 to Doutney discloses a method and apparatus for cleaning a photoconductive surface. The apparatus includes an AC charged cleaning brush and a cleaning blade located immediately downstream from the cleaning brush. The cleaning brush is located downstream from a sheet separator and serves the purpose of removing residual toner from the photoconductive surface as well as any residual charge. The cleaning blade subsequently removes any remaining toner particles from the surface.
U.S. Pat. No. 3,801,197 to Akiyama et al. discloses a color electrophotographic copying apparatus including a cleaning device having successive cleaning means.
U.S. Pat. No. 3,795,025 to Sadamitsu, discloses an apparatus for cleaning an electrophotographic photoreceptor. The apparatus includes a pair of brushes rotating in opposite directions. The rotating brushes are enclosed in a brush box and a vacuum system removes toner from the brushes and the inside of the brush box.